1. Field of Invention
This invention relates to a screen exchanging device in a plasticizing apparatus to be used in an extrusion molding machine, an injection molding machine, etc.
2. Related Art
One example of a screen exchanging device in the conventional extrusion molding machine will be explained hereunder.
As shown in FIG. 6, the screen exchanging device of the conventional type includes a housing 100 having a through hole 102, a blind flange 106 detachably provided at one end of the housing 100, a slide bar 105 slidably inserted in the through hole 102 in an axial direction from the other end of the housing 100. In a filter chamber 107 formed between a distal end face of the slide bar 105 and the blind flange 106, is arranged filter means 108 which will be described below. On opposite side walls of the housing 100, are respectively formed an inlet 103 and an outlet 104 which communicate with each other.
The filter means 108 consists of a container plate 109 in a form of a perforated plate and fixed to the distal end of the slide bar 105, and a plurality of cylindrical screen pack cartridges 108a detachably attached to the container plate 109 at a face thereof opposite to the slide bar side. The screen pack cartridge 108a is composed of a cylindrical breaker plate and a screen net which covers an outer peripheral wall thereof.
In this screen exchanging device, a molten resin flowing from the inlet 103 into the filter chamber 107 is filtered through a plurality of the screen pack cartridges 108a to remove foreign objects, and then flows through the perforated container plate 109 to be discharged from the outlet 104. When the foreign objects are accumulated and a loss in pressure has exceeded the determined value, the screen pack cartridges 108a will be exchanged. On this occasion, after removing the blind flange 106 of the housing 100, a hydraulic cylinder 111 is actuated to project its rod 111a in order to push the slide bar 105, thereby to cause the distal end of the slide bar 105 to project from the one end of the housing 100, thus allowing the screen pack cartridges 108a to be exchanged with new ones (JP-A-7-299310).
According to the above described conventional art, because the cylindrical screen pack cartridges are arranged on one face of the container plate, only a limited number of the screen pack cartridges can be arranged, and when exchanging the screen, it takes a lot of time and efforts to attach and detach the screen pack cartridges to and from the container plate. Moreover, since the filtered foreign objects are accumulated in the filter chamber, there has been an additional problem that the foreign objects accumulated in the filter chamber must be removed at the same time.